The present invention relates to a flywheel of a vehicle for use in a power train assembly, and more particularly, to a dual-mass flywheel that provides damping effects under various vibration conditions.
Generally, a flywheel is used to dampen torsional vibrations between an internal combustion engine and a power train. That is, the flywheel is an apparatus that acquires rotational force during a power stroke and decreases a rotational speed change by inertial force during other strokes. The flywheel is provided with a primary mass connectable to a secondary mass, the primary mass being non-rotatably affixed to an output element (such as a crankshaft) of an engine, and the secondary mass being connectable to an input shaft of a transmission in response to engagement of a friction clutch. The primary mass and the secondary mass can rotate relative to each other in a predetermined range, and therefore even though torsional vibrations occur because of a sudden engine torque change, a sudden change in rotational speed can be prevented so that the torsional vibrations do not transmit to other components of the vehicle.
In the above-stated flywheel, the secondary mass performs as a dynamic damper such that torsional vibrations of a drive system can be decreased. The secondary mass is connected to the primary mass through a spring.
As shown in FIG. 1a, a conventional flywheel includes a primary mass 110 and a secondary mass (not shown) that is rotatable relative to the primary mass 110. The secondary mass is rotatably connected to the primary mass 110 through an arc-shaped spring 120 that is fixed to the primary mass 110.
If the primary mass 110 rotates, the spring 120 pushes a drive plate (not shown) that is fixed to the secondary mass by riveting so that the secondary mass rotates. Then, a clutch that is fixed to the secondary mass starts to rotate.
FIG. 1b shows another conventional flywheel that comprises a spring 120xe2x80x2 that is arranged in a radial direction of a primary mass 110xe2x80x2. If a drive plate (not shown) that is fixed to a secondary mass (not shown) rotates, the secondary mass causes tension force on the spring 120xe2x80x2.
FIG. 1c shows yet another conventional flywheel that comprises a primary mass 110xe2x80x3. A plurality of linear springs 120xe2x80x3 are circularly disposed in the primary mass 110xe2x80x3.
However, the above-stated conventional flywheels can operate satisfactorily only under specific circumstances. Operation of these flywheels depends only on engine torque regardless of engine speed, and therefore it is difficult to obtain satisfactory damping effects under various vibration characteristics.
The present invention provides a dual mass flywheel in which damping force varies with change of engine speed such that satisfactory damping effects under various vibration conditions can be obtained.
In a preferred embodiment of the present invention, a primary mass is connected to an engine crankshaft. The primary mass includes a damping chamber extending along its circumferential direction. A secondary mass is supported for rotation relative to the primary mass and adapted to be coupled to a transmission input shaft. A drive plate is coupled to said secondary mass and a torsional vibration damping device yieldingly couples the secondary mass to the primary mass. Preferably, in the torsional vibration damping device, a plurality of ball members move along the damping chamber by centrifugal force. A plurality of ball guide members force the ball members to contact the primary mass. Each of the ball guide members are arranged to be rotatable with the drive plate. A plurality of resilient members support each of the ball members on both sides. A drive guide transmits rotational force of the drive plate to the resilient members and is arranged to rotate with the drive plate.
Preferably, the dual mass flywheel further comprises a plurality of joint guides being disposed between the ball members and the resilient members, with the joint guides having the resilient members forced along their longitudinal axes.
In another preferred embodiment of the present invention a primary mass adapted to be attached to a crankshaft for rotation. The primary mass has two sheet metal components defining a damping chamber extending along its circumferential direction. A secondary mass is connectable to a transmission input shaft, with the secondary mass being rotatable relative to the primary mass. A torsional vibration damping device yieldingly couples the secondary mass to the primary mass. In this embodiment, in the torsional vibration damping device, a plurality of resilient members are disposed in the damping chamber of the primary mass along its circumferential direction. A roller is disposed between the resilient members, the roller being arranged to be movable in a radial and a circumferential direction. A drive plate is fixedly coupled to the secondary mass, compressing the resilient members when there is a rotational deviation between the primary mass and the secondary mass.
Preferably, the dual mass flywheel further comprises a joint guide disposed between the roller and the resilient members so that a force compressing the resilient members acts along a longitudinal axis of the resilient members. A roller guide is also disposed between the roller and an inner wall of the damping chamber so as to guide movements of the roller. And a drive guide is disposed between the said resilient members and the drive plate.